Swift Increase font size of the UITextview,how?

Swift 4,5

yourTextView.font = .systemFont(ofSize: 16)

I don't think there's a method named increaseSize(). May be you've find some UIFont or UITextView category.

The official UIFont class document doesn't reveal any such method.

Additionally you can increase the font like this:

textview.font = UIFont(name: textview.font.fontName, size: 18)

The above statement will simply set the existing font size to 18, change it to whatever you want.

However if you want some method like you've posted, you can introduce your own category like this:

extension UITextView {
    func increaseFontSize () {
        self.font =  UIFont(name: self.font.fontName, size: self.font. pointSize+1)!
    }
}

Swift 2 & 3:

import UIKit
extension UITextView {
    func increaseFontSize () {
        self.font =  UIFont(name: (self.font?.fontName)!, size: (self.font?.pointSize)!+1)!
    }
}

and simply import this to wherever you want to use like this:

textview.increaseFontSize()

it'll increase the font by 1 every time you call it..

For the system font, this also works:

yourTextView.font = .systemFontOfSize(16)